The present invention relates to a ball screw including a screw shaft and a nut that are meshed with each other via a number of balls, and in particular to a ball screw having an end deflector for the balls fitted at least in one end of the nut.
The ball screw typically includes a screw shaft having a thread formed on an outer circumference thereof, a nut having a central bore and defining a thread corresponding to the thread on the screw shaft on an inner circumferential surface thereof so as to define a spiral raceway, and a plurality of steel balls received in the raceway so that the rotational motion of the screw shaft may be converted into a linear motion of the nut in a highly efficient and accurate manner. The balls exiting from one end the raceway have to be returned the other end of the raceway typically via a ball return hole passage which may be formed by an external tube member or formed in the nut itself In either case, an end deflector is formed in each axial end of the nut to pass the steel balls from the raceway to the ball return hole passage or vice versa.
JP 2007-24305A discloses a ball screw in which an end deflector consisting of two pieces is attached to each axial end of the nut by using screws. JP 2011-241852A discloses a plastic end deflector which is simply fitted into a recess formed in each axial end of the nut. A bonding agent and a retaining ring are mentioned as possible means for fixedly retaining the end deflector in the recess. An engagement feature is also disclosed as a means for retaining the end deflector which is configured to be fitted into a recess in the nut from the outer circumferential surface of the nut.
JP 2007-40469A discloses a plastic end deflector which is provided with a resilient circumferential projection fitted into a corresponding slot in the nut so as to produce a resilient torque urging the end deflector against the opposing inner circumferential surface of the recess receiving the end deflector. JP 4335222B discloses a ball screw which uses a retainer ring for securing an end deflector received in an end deflector receiving recess of the nut.
These conventional retaining structures for an end deflector either require highly complex structures or may not be suitable for adequately securely and accurately retaining the end deflector. Therefore, there is a need for a ball screw which is incorporated with an improved arrangement for securing an end deflector.